Solving the PUBLIC_BACKEND_SERVER_URL is not exported error During Docker Build Despite Being Set in .env File in SvelteKit Project

If you’re a SvelteKit enthusiast, you might have stumbled upon a frustrating error during Docker build: “PUBLIC_BACKEND_SERVER_URL is not exported”. Don’t worry, you’re not alone! In this article, we’ll delve into the world of environment variables, .env files, and Docker builds to provide a comprehensive solution to this issue.

What is PUBLIC_BACKEND_SERVER_URL and why is it important?

PUBLIC_BACKEND_SERVER_URL is an environment variable in SvelteKit that allows your frontend to communicate with your backend server. It’s essential for making API calls, authentication, and other backend-related tasks. In a production environment, you need to set this variable to ensure your app functions correctly.

The role of .env files in SvelteKit

In SvelteKit, .env files play a crucial role in managing environment variables. These files contain sensitive data, such as API keys, database credentials, and other configuration settings. When you create a .env file in the root of your project, SvelteKit automatically loads the variables into the application.

Setting environment variables in .env files

To set environment variables in a .env file, simply add the variable name followed by its value, separated by an equals sign (=). For example:

PUBLIC_BACKEND_SERVER_URL=https://example.com/api

In this example, we’re setting the PUBLIC_BACKEND_SERVER_URL variable to https://example.com/api.

The issue: PUBLIC_BACKEND_SERVER_URL is not exported during Docker build

Now, let’s dive into the issue at hand. When you try to build a Docker image for your SvelteKit application, you might encounter an error saying “PUBLIC_BACKEND_SERVER_URL is not exported”. This is frustrating because you’ve already set the variable in your .env file!

Understanding the problem

The issue arises because Docker doesn’t automatically load environment variables from .env files during the build process. Instead, it relies on the environment variables being set in the Dockerfile or through the command line.

Solving the error: 3 approaches

Don’t worry; we’ve got you covered! Here are three approaches to solve the “PUBLIC_BACKEND_SERVER_URL is not exported” error during Docker build:

Approach 1: Setting environment variables in the Dockerfile

One way to solve the issue is to set the environment variable directly in the Dockerfile. You can do this by adding the following line:

ENV PUBLIC_BACKEND_SERVER_URL=https://example.com/api

This sets the PUBLIC_BACKEND_SERVER_URL variable to https://example.com/api during the Docker build process.

Approach 2: Using the –build-arg flag with Docker

Another approach is to pass the environment variable as a build argument when running the Docker build command. You can do this by using the –build-arg flag:

docker build --build-arg PUBLIC_BACKEND_SERVER_URL=https://example.com/api -t my-sveltekit-app .

This sets the PUBLIC_BACKEND_SERVER_URL variable to https://example.com/api during the Docker build process.

Approach 3: Using a separate environment file for Docker

PUBLIC_BACKEND_SERVER_URL=https://example.com/api

Then, in your Dockerfile, load the environment variables from the docker.env file:

FROM node:14

WORKDIR /app

ENV PUBLIC_BACKEND_SERVER_URL

COPY docker.env .

# Rest of the Dockerfile...

This approach allows you to keep your environment variables separate from your .env file and load them specifically for the Docker build process.

Conclusion

In this article, we explored the “PUBLIC_BACKEND_SERVER_URL is not exported” error during Docker build in SvelteKit projects. We discussed the importance of PUBLIC_BACKEND_SERVER_URL, the role of .env files, and three approaches to solve the error: setting environment variables in the Dockerfile, using the –build-arg flag, and creating a separate environment file for Docker.

By following these solutions, you’ll be able to successfully build your Docker image and ensure that PUBLIC_BACKEND_SERVER_URL is properly set for your SvelteKit application.

Troubleshooting tips

If you’re still encountering issues, here are some troubleshooting tips:

• Check that your .env file is in the correct location (root of the project) and that the variable is set correctly.
• Verify that you’re using the correct Docker build command and that the –build-arg flag is being used correctly.
• Make sure that your Dockerfile is loading the environment variables correctly.

Final thoughts

Solving the “PUBLIC_BACKEND_SERVER_URL is not exported” error during Docker build might seem challenging, but by understanding the role of environment variables, .env files, and Docker builds, you can overcome this obstacle. Remember to choose the approach that best fits your project’s needs, and don’t hesitate to reach out if you encounter any further issues.

Happy coding, and may the Docker builds be with you!

Approach	Pros	Cons
Setting environment variables in the Dockerfile	Easy to implement, straightforward	Hardcodes the environment variable in the Dockerfile
Using the –build-arg flag with Docker	Flexibility to pass environment variables during build, easy to manage	Requires additional command-line arguments, may lead to typos
Using a separate environment file for Docker	Separation of concerns, easy to manage environment variables for Docker	Requires an additional file, may add complexity to the project structure

This table provides a summary of the three approaches, highlighting their pros and cons. Choose the approach that best fits your project’s needs and requirements.

Frequently Asked Question

Are you stuck with the “PUBLIC_BACKEND_SERVER_URL is not exported error” during Docker build despite setting it in your .env file in your SvelteKit project? Worry not, we’ve got you covered! Here are some frequently asked questions and answers to help you troubleshoot and resolve the issue.